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import { pull } from 'lodash';
import { Observable } from 'rxjs';
export type Subscriber<TData> = (data: TData) => void;
export interface ISubscriptionLine<TData> {
readonly value: undefined | TData;
next(value: TData): void;
}
export class SubscriptionLine<TData> implements ISubscriptionLine<TData> {
private _current: TData | undefined = undefined;
private _observers: Subscriber<TData>[] = [];
constructor(
private config?: { destroyable?: (value: TData | undefined) => boolean }
) {}
subscribe(subscriber: Subscriber<TData>): void {
this._observers.push(subscriber);
if (this._current !== undefined) {
subscriber(this._current);
}
}
unsubscribe(subscriber: Subscriber<TData>): void {
if (!this._observers.includes(subscriber)) return;
pull(this._observers, subscriber);
}
get value(): TData | undefined {
return this._current;
}
next(value: TData): void {
this._current = value;
this._observers.forEach((observer) => observer(value));
}
get destroyable(): boolean {
const customDestroyable = this.config?.destroyable;
return (
this._observers.length === 0 &&
(customDestroyable != null ? customDestroyable(this._current) : true)
);
}
}
export class SubscriptionHub<TKey, TData> {
private keyToString: (key: TKey) => string;
private setup?: (
key: TKey,
line: ISubscriptionLine<TData>
) => (() => void) | void;
private destroyable?: (key: TKey, value: TData | undefined) => boolean;
private readonly subscriptionLineMap = new Map<
string,
SubscriptionLine<TData>
>();
private cleanTimerId = 0;
// setup is called after creating line and if it returns a function as destroyer, then when the line is destroyed the destroyer will be called.
constructor(config?: {
keyToString?: (key: TKey) => string;
setup?: (key: TKey, line: ISubscriptionLine<TData>) => void;
destroyable?: (key: TKey, value: TData | undefined) => boolean;
}) {
this.keyToString =
config?.keyToString ??
((value): string => {
if (typeof value === 'string') return value;
else
throw new Error(
'Default keyToString function only pass string value.'
);
});
this.setup = config?.setup;
this.destroyable = config?.destroyable;
}
private cleanLines(): void {
const toDelete: string[] = [];
for (const [key, line] of this.subscriptionLineMap.entries()) {
if (line.destroyable) {
toDelete.push(key);
}
}
if (toDelete.length === 0) return;
for (const key of toDelete) {
this.subscriptionLineMap.delete(key);
}
if (this.subscriptionLineMap.size === 0) {
window.clearInterval(this.cleanTimerId);
this.cleanTimerId = 0;
}
}
private createLine(key: TKey, useSetup = true): SubscriptionLine<TData> {
const keyString = this.keyToString(key);
const { setup, destroyable } = this;
const newLine = new SubscriptionLine<TData>({
destroyable:
destroyable != null ? (value) => destroyable(key, value) : undefined,
});
this.subscriptionLineMap.set(keyString, newLine);
if (useSetup) {
setup?.(key, newLine);
}
if (this.subscriptionLineMap.size === 1) {
this.cleanTimerId = window.setInterval(this.cleanLines.bind(this), 20000);
}
return newLine;
}
subscribe(key: TKey, subscriber: Subscriber<TData>): void {
const keyString = this.keyToString(key);
const line =
this.subscriptionLineMap.get(keyString) ?? this.createLine(key);
return line.subscribe(subscriber);
}
unsubscribe(key: TKey, subscriber: Subscriber<TData>): void {
const keyString = this.keyToString(key);
const line = this.subscriptionLineMap.get(keyString);
return line?.unsubscribe(subscriber);
}
getObservable(key: TKey): Observable<TData> {
return new Observable((observer) => {
const f = (data: TData): void => {
observer.next(data);
};
this.subscribe(key, f);
return () => {
this.unsubscribe(key, f);
};
});
}
getLine(key: TKey): ISubscriptionLine<TData> | null {
const keyString = this.keyToString(key);
return this.subscriptionLineMap.get(keyString) ?? null;
}
getLineOrCreateWithoutSetup(key: TKey): ISubscriptionLine<TData> {
const keyString = this.keyToString(key);
return (
this.subscriptionLineMap.get(keyString) ?? this.createLine(key, false)
);
}
}
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